Problem 16 - Chemistry The Molecular Nature of Matter

Question

What chemical reaction takes place when solid sodium sulfide is dissolved in water? Write the chemical equation.

Step-by-Step Solution

Answer

\( \text{Na}_2\text{S} (s) + \text{H}_2\text{O} (l) \rightarrow 2\text{Na}^+ (aq) + \text{S}^{2-} (aq) \)

Step 1: Identify the Reactants

The reactants in this scenario are solid sodium sulfide (Na2S) and water (H2O).

Step 2: Predict the Dissociation

Sodium sulfide is an ionic compound and will dissociate into sodium ions (Na+) and sulfide ions (S2-) when dissolved in water.

Step 3: Write the Chemical Equation

The dissociation of sodium sulfide in water can be represented by the following chemical equation: \( \text{Na}_2\text{S} (s) + \text{H}_2\text{O} (l) \rightarrow 2\text{Na}^+ (aq) + \text{S}^{2-} (aq) \)

Key Concepts

Chemical Equations

Understanding a chemical equation is crucial for students as it offers a way to visualize chemical reactions. A chemical equation is a symbolic representation where the reactants are listed on the left side, while the products are on the right. Each is separated by an arrow indicating the direction of the reaction. In our scenario, the chemical equation for the dissolution of sodium sulfide in water is:\[\begin{equation} \text{Na}_2\text{S} (s) + \text{H}_2\text{O} (l) \rightarrow 2\text{Na}^+ (aq) + \text{S}^{2-} (aq) \end{equation}\]This equation conveys not only the substances involved but also their physical states – solid (s), liquid (l), and aqueous (aq). Furthermore, it indicates the stoichiometry of the reaction, which means the ratio of reactants and products. In this case, one formula unit of sodium sulfide yields two sodium ions and one sulfide ion upon dissolution. To improve one's understanding, it is vital to balance the chemical equation ensuring that the number of atoms for each element is the same on both sides of the reaction.

Ionic Compounds

Ionic compounds, such as sodium sulfide (\[\begin{equation} \text{Na}_2\text{S} \end{equation}\]), are made up of ions that are held together by strong electrostatic forces known as ionic bonds. These ions are atoms or molecules that have lost or gained electrons, resulting in a net charge: Na+ has lost one electron, S2- has gained two electrons. When ionic compounds dissolve in water, they split into their respective ions in a process called dissociation.

This is an essential concept for students to grasp because it explains many of the properties of ionic compounds, such as their high melting and boiling points, and their ability to conduct electricity when molten or in solution. Knowing how to predict these behaviors from the chemical formula of an ionic compound can be very helpful in understanding the nature of these substances.

Reaction in Aqueous Solution

A reaction in aqueous solution takes place when compounds dissolve in water and interact with one another. Dissolution is just one form of such reactions, where a solute (in our case, sodium sulfide) breaks down to form ions that are distributed throughout the solvent (water). This process significantly changes the solute's properties and often allows for it to participate in further chemical reactions.

The dissociation of sodium sulfide in water is a typical example of what occurs when an ionic compound reacts in an aqueous solution. The water molecules surround the ions from the solid lattice, stabilizing them in solution and allowing them to move freely. This is important in many fields, from biochemistry, where water is the medium for countless reactions, to industrial processes that rely on reactions in solution. Recognizing the various types of reactions that can occur in an aqueous environment, like precipitation, acid-base, and redox reactions, further builds a student's chemical literacy and practical understanding of everyday chemical phenomena.